OBJECTIVE: To describe the clinical presentation a group of patients with juvenile onset of Huntington disease. METHOD: All patients were interviewed following a structured clinical questioner. Patients were genotyped for the trinucleotide cytosine-adenine-guanine (CAG) repeat in the Huntington Disease gene. High resolution brain MRI was performed in all patients. RESULTS: We identified 4 patients with juvenile onset of disease among 50 patients with Huntington disease followed prospectively in our Neurogenetics clinic. Age at onset varied from 3 to 13 years, there were 2 boys, and 3 patients had a paternal inheritance of the disease. Expanded Huntington disease allele sizes varied from 41 to 69 trinucleotide repeats. The early onset patients presented with rigidity, bradykinesia, dystonia, dysarthria, seizures and ataxia. MRI showed severe volume loss of caudate and putamen nuclei (p=0.001) and reduced cerebral and cerebellum volumes (p=0.01). CONCLUSION: 8% of Huntington disease patients seen in our clinic had juvenile onset of the disease. They did not present with typical chorea as seen in adult onset Huntington disease. There was a predominance of rigidity and bradykinesia. Two other important clinical features were seizures and ataxia, which related with the imaging findings of early cortical atrophy and cerebellum volume loss.